1. Field of the Invention
The present invention relates to a depression container that is capable of maintaining the internal pressure under a predetermined value, and more particularly to a depression container equipped with an air pump that can be activated when the internal pressure in the depression container is below a predetermined value.
2. Description of the Related Art
A typical depression container includes a one-way valve and a user may manually operate a hand air pump to draw air out of the container via the one-way valve. The internal pressure of the container is thus reduced to a relatively low valve (almost vacuum). This reduces the risk of the articles in the container from being wetted or contaminated by dust or bacteria, thereby lengthening the preserve time. It is, however, troublesome and labor-intensive for the user to reciprocatingly operate the hand air pump for many times. In addition, the user cannot know the exact internal pressure in the depression container. Furthermore, the depression container cannot provide an absolute sealing effect such that the internal pressure in the depression container may rise after a period of time and thus adversely affect preservation of the articles in the depression container.
It is an object of the present invention to provide a depression container that may automatically draw air out of the depression container after a cover is attached to enclose an open end of the depression container. The internal pressure of the depression container is reduced to a predetermined value.
It is another object of the present invention to provide a depression container that clearly shows the value of the internal pressure. The depression container also allows the user to reset the internal pressure desired for preserving articles.
It is a further object of the present invention to provide a depression container that may maintain the internal pressure thereof under a predetermined valve for a long time.
In accordance with a first aspect of the invention, a depression container comprises:
a vessel including a compartment with an open end;
a cover for enclosing the open end of the vessel and thus sealing the compartment;
an air pump for drawing air out of the compartment of the vessel; and
a pressure-activated switch for controlling on/off of the air pump;
the pressure-activated switch being capable of detecting an internal pressure in the compartment of the vessel, the air pump being turned on when the internal pressure is higher than a predetermined first pressure value, the air pump being turned off when the internal pressure is lower than a predetermined second pressure value that is smaller than the predetermined first pressure value.
In accordance with a second aspect of the invention, a depression container comprises:
a vessel including a compartment with an open end;
a cover for enclosing the open end of the vessel and thus sealing the compartment;
an air pump for drawing air out of the compartment of the vessel; and
a pressure-activated switch for controlling on/off of the air pump;
the pressure-activated switch detecting a pressure difference resulting from a closing motion of the cover on the vessel and turning the air pump on to thereby draw air out of the compartment of the vessel, the air pump being turned off when an internal pressure in the compartment detected by the pressure-activated switch is lower than a predetermined pressure value.
Thus, the air pump is activated by a pressure difference resulting from the closing motion of the cover, and the pump is deactivated after the internal pressure in the vessel is reduced to a first predetermined pressure value. When the internal pressure rises and exceeds a second predetermined pressure value higher than the first predetermined value, the pump is activated again until the internal pressure is reduced to the first predetermined pressure value. Thus, the articles in the vessel can be preserved for a long time by means of maintaining the internal pressure in the vessel under a predetermined low pressure suitable for preservation of articles.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.